JPH0786650A - Laminated actuator - Google Patents

Abstract

PURPOSE:To provide a laminated actuator that provides displacement amount of high precision over a wide displacement range. CONSTITUTION:Relating to a laminated actuator l, a digital displacement element 20 which, consisting of an electric field excitation phase transition material, makes phase transition from anti-ferroelectric phase to ferroelectric phase due to electric field application, for a specified displacement amount to be caused, or a laminated digital displacement element 2 wherein the elements 20 are laminated in the direction of displacement, and arm analogue displacement element 3 which, consisting of a piezoelectric or electrostrictive material, can change at least to a specified displacement amount according to applied electric field, are laminated in the direction of displacement elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator that uses a piezoelectric / electrostrictive ceramic material to generate a displacement by applying an electric field, and relates to a stepwise displacement for each predetermined unit amount and a continuous displacement of less than a predetermined unit amount. The present invention relates to a laminated actuator capable of obtaining a highly accurate amount of displacement over a wide range of displacement by combining various displacements.

[0002]

2. Description of the Related Art A laminated actuator in which a large amount of displacement is obtained by laminating a plurality of piezoelectric ceramic green sheets each having an electrode formed on the surface thereof is known from JP-A-62-291080. There is.

[0003]

Since the piezoelectric element has a small displacement amount, it is necessary to significantly increase the number of stacked layers or to use a displacement magnifying mechanism together in order to obtain a larger displacement amount. If the number of laminated layers is significantly increased, the number of internal electrodes taken out increases and the actuator becomes large. Further, since the characteristic variation per layer (for example, the variation of the displacement amount due to the variation of the thickness) is multiplied by the number of laminated layers, it may be difficult to maintain the displacement accuracy. When the displacement magnifying mechanism is also used, the applied electric field must be precisely controlled according to the magnifying power in order to maintain the displacement accuracy.

The present invention has been made to solve such a problem, and an object thereof is to provide a laminated actuator capable of obtaining a highly accurate displacement amount over a wide displacement range.

[0005]

In order to solve the above-mentioned problems, the laminated actuator according to claim 1 is made of an electric field-excited phase-transition material and undergoes a phase transition from an antiferroelectric phase to a ferroelectric phase by application of an electric field, thereby causing a predetermined displacement. A digital displacement element that produces an amount or a laminated digital displacement element in which the digital displacement element is laminated in the displacement direction, and an analog displacement that is made of a piezoelectric material or an electrostrictive material and can be displaced to at least the predetermined displacement amount according to an applied electric field. The element and the displacement element are laminated in the displacement direction of each displacement element. The laminated actuator according to claim 2 is a digital displacement element made of a piezoelectric / electrostrictive material having a displacement memory effect by causing a phase transition from an antiferroelectric phase to a ferroelectric phase when an electric field is applied, and an analog displacement when an electric field is applied. An analog displacement element made of a piezoelectric / electrostrictive material is laminated in the displacement direction.

[0006]

When a digital displacement element is applied with an electric field higher than a predetermined value, the antiferroelectric phase undergoes a phase transition from the ferroelectric phase to a predetermined amount of displacement. The digital displacement layered element in which a plurality of layers of this digital displacement element are layered can obtain a stepwise displacement in a predetermined displacement amount unit. By combining the digital displacement element or the digital displacement layered element with at least the analog element capable of continuously varying the predetermined displacement amount, continuous displacement can be obtained over a wide displacement range. A wide range of displacements can be obtained only by combining the digital displacement element and the analog displacement element.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic structural diagram of a laminated actuator according to the present invention. The laminated actuator 1 according to the present invention is formed by laminating a laminated digital displacement element 2 and an analog displacement element 3 via an insulating material 4. The insulating material 4 separates the electrode 20c on one end side of the laminated digital displacement element 2 and the electrode 3b on one end side of the analog displacement element 3 so that the power source 5 for driving the digital displacement element and the power source 6 for driving the analog displacement element are completely separated. It is inserted when separating, and the electrodes 3b and 20
When the configuration is such that c is common and one end side of each of the driving power supplies 5 and 6 is commonly connected, the insulating material 4 is not necessary.

The laminated digital displacement element 2 has electrodes 20 on the surface of a displacement element body 20a made of an electric field excitation type phase transition material.
A plurality of (6 in FIG. 1) digital displacement elements 20 having b formed thereon are laminated. An electrode 20c on the other end side is formed on a green sheet (corresponding to the element body 20a) of the electric field excitation type phase change material, which has electrodes 20b formed on the surface thereof, and is then integrated by hot pressing. Then, the laminated digital displacement element 2 may be manufactured by cutting into a predetermined shape and then sintering. As the electric field excitation phase transition material, P
P containing b, Ba, Nb, Zr, Sn, and Ti as composition components
BNZST-based or PNZST-based piezoelectric / electrostrictive materials can be used.

The electrodes 20b are alternately taken out and connected to the positive electrode side and the negative electrode side of the digital displacement element driving power source 4 via the switches S0 to S6, respectively. The digital displacement element driving power supply 5 supplies a DC high voltage sufficient for causing a phase transition to each digital displacement element 20.

As the analog displacement element 3, a displacement element body 3a made of a piezoelectric material such as PZT and provided with electrodes 3b and 3c is used. The analog displacement element 3 is
You may use the thing of the laminated structure shown in FIG. Each electrode 3
b and 3c are connected to the positive and negative power source output terminals of the variable displacement type analog displacement element driving power source 5, respectively.

FIG. 2 is an explanatory view showing a schematic structure of a digital displacement element and its displacement characteristic. When the electric field E generated in the displacement element body 20a by the voltage V applied between the electrodes 20b and 20c shown in FIG. 2A exceeds the phase transition electric field ET (for example, 3 KV / m) shown in FIG. 2B, Phase transition from antiferroelectric phase AF to ferroelectric phase FE
A displacement (ΔL / L) corresponding to the length L in the displacement direction of is generated. This displacement has a hysteresis characteristic and returns to the original value by making the applied electric field E zero (characteristic shown by the solid line in FIG. 2B), but it does not return unless the electric field of the opposite polarity is applied. There is a displacement memory type (characteristic shown by a dotted line in FIG. 2B). In this embodiment, the former one is used. In addition,
When the latter one is used, the electric field in the opposite direction is applied when returning the displacement (see FIG. 6).

FIG. 3 is an explanatory view showing a compound displacement of the laminated actuator according to the present invention. Digital displacement element 20
Causes a predetermined amount of displacement due to the phase transition, so that the laminated digital displacement element 2 in which the digital displacement elements 20 are laminated as shown in FIG. 1 depends on the number of the digital displacement elements 20 to which the phase transition electric field ET is applied. As shown by the characteristic D in FIG. 3, the displacement amount can be changed stepwise. Since the analog displacement element 3 produces a continuous displacement according to the applied electric field, the digital displacement element 20 and the analog displacement element 3
By combining and, it is possible to obtain the composite displacement characteristic shown by the characteristic F in FIG.

A specific example of displacement characteristics of the laminated actuator 1 shown in FIG. 1 will be described. An electric field of, for example, 1 KV (kilovolt) / mm (millimeter) is applied to the laminated digital displacement element 2 in which six (a) to (f) digital displacement elements 20 having a displacement amount of 0.5 μm (micrometer) are laminated. The analog displacement elements 3 that generate a displacement of 0.5 μm are stacked in the displacement direction of each displacement element.

With switch S0 closed, switch S
When 1 is closed and an electric field sufficient to cause a phase transition is applied between both electrodes of the digital displacement element 20 indicated by reference numeral (a), the digital displacement element (a) causes a phase transition and a displacement of 0.5 μm occurs. The displacement disappears when the switch S1 is opened to stop the application of the electric field. When the switch S2 is closed while the switch S1 is closed, the electric field is also applied to the element (b), so that the two elements (a) and (b) are displaced by the phase transition, resulting in a displacement of 1 μm in total. . Similarly, switch S3
By sequentially closing S6 to S6, the number of elements to which an electric field is applied increases, and a displacement of 3 μm occurs when all the switches are closed. The digital displacement elements 20 are arranged in the above order.
The switch S0 does not have to be provided when the driving is performed.

On the other hand, since the displacement amount of the analog displacement element 3 can be continuously controlled by varying the applied voltage, it is necessary to open / close the switches S1 to S6 and adjust the applied voltage of the analog displacement element 3. Therefore, a wide displacement range can be obtained.

FIG. 4 is a graph showing a specific example of displacement characteristics of the laminated actuator shown in FIG. The horizontal axis represents the electric field applied to the analog displacement element, and the vertical axis represents the displacement amount. The parameter n is the number of digital displacement elements that generate a predetermined amount of displacement by applying an electric field.

When the laminated actuator 1 is used as an output element of a displacement or position control servo system,
The displacement amount of the analog displacement element 3 having a margin with respect to the displacement amount of the digital displacement element 20 is used, and as shown by the dotted line in FIG. It is desirable that the range can follow.

FIG. 5 is a schematic structural diagram of a monolithic laminated actuator according to the present invention. The laminated actuator 41 is formed by integrally laminating a laminated digital displacement element 41 and a laminated analog displacement element 42. A plurality of layers (8 layers in FIG. 5) having electrodes 50b formed on the surface of the green sheet of the electric field excitation type phase transition material constituting the digital displacement element body 50a are laminated, and the analog displacement element body 60a is further formed thereon. A plurality of layers (7 layers in FIG. 5) in which the electrodes 60b are formed on the green sheet of piezoelectric ceramics are laminated by heat pressing or the like to be integrated, and the electrodes 60c are formed on the integrated body to form a predetermined shape. After the cutting, the displacement elements 41 and 42 are integrally manufactured by sintering.

Then, each of the electrodes 50b and 60b is connected to the common external electrode 43 that is taken out alternately, and the other electrode 60b of the analog displacement element 60 is connected to the analog external electrode 44, and the common external electrode 43 and the analog external electrode 44 are connected. An electric field is applied from the analog element driving power source 6 to the external electrode 44. The other electrode 5 of the digital displacement element 50
0b is connected to the digital displacement element driving power source 5 via the respective switches SA to SD. Each switch S
One drive unit is composed of two upper and lower digital displacement elements sandwiching the electrode 50b connected to A to SD, for example, element (a) and element (b), element (c) and element (d).
For example, when the switch SA is closed, an electric field is applied to the element (a) and the element (b), and the two elements (a) and (b) are displaced by the phase transition.

Incidentally, a digital external electrode (not shown) may be provided on the side surface of the laminated digital displacement element 41 and, for example, four digital displacement elements may be connected as one unit. The number of stacked layers of the displacement elements 50 and 60 and the stacking order of the stacked digital displacement element 41 and the stacked analog displacement element 42 are arbitrary. The maximum displacement width of the stacked analog displacement element 42 is set such that the number of stacked layers is set so that the unit displacement amount determined by the driving unit of the digital displacement element can be covered, or the analog displacement element driving power source 6
The maximum supply voltage of is set.

FIG. 6 is a schematic structural diagram of a displacement memory type laminated actuator according to the present invention. In the displacement memory type laminated actuator 70, the displacement element body 80a of the digital displacement element 80 is provided with a piezoelectric or electrostrictive material (for example, P that has a displacement memory type hysteresis characteristic shown in FIG. 2B).
b, Ba, Nb, Zr, Sn, Ti system) and the laminated analog displacement element 42 are integrally laminated.

Further, the laminated digital displacement element 71 is provided with two digital external electrodes 72 and 73 on its side surface, and four digital displacement elements (element (a) to element (d), element (e) to element ( H)) is one unit and an electric field is applied.

Each of the switches SY and SZ for applying an electric field is of a switching type having a neutral position. When switched to one, a displacement driving voltage from the digital displacement element driving power source 5 is supplied to the other. When the switching is performed, the digital displacement element restoration power supply 90 supplies a voltage having a polarity opposite to that at the time of driving.

When the digital displacement element having the hysteresis characteristic shown by the dotted line in FIG. 2B is used, an electric field equal to or higher than the phase transition electric field ET is continuously applied and the displacement amount corresponding to the displacement rate when the electric field is applied is a unit. The method of controlling the displacement as the amount of change corresponds to the holding change rate in the state where no electric field is applied by setting the switches SY and SZ to the neutral position after applying an electric field equal to or higher than the phase transition electric field ET for a time period during which the phase transition occurs. There are a method of setting a holding change amount as a unit change amount and a method of using a unit change amount in combination with these two types.

Particularly, in the displacement control in which the amount of change in holding is used as a unit change, the amount of displacement as a digital displacement element is maintained until the power supply 90 for restoration is supplied even if the application of the driving electric field cannot be normally performed. it can. Therefore, in a device or the like configured to give a predetermined displacement amount as a so-called bias amount and perform servo control or the like on the analog displacement element side from the bias amount, provide a fail-safe configuration even if an abnormality occurs in the driving power source. Is possible. Also, when the power of the displacement control system is newly turned on, the adjustment position for each predetermined unit amount in the previous displacement control can be held in each digital displacement element, so that from the initial position to the desired position. It becomes possible to follow in a shorter time than the time to perform follow-up control, and since the displacement amount at the start of new control is close to the previous displacement amount, the operating state at power-on etc. is the same as the previous state. The advantage that they are almost the same can be obtained.

FIG. 7 is a block diagram showing a specific example of a power supply drive control device for a laminated actuator. This power supply drive device 100 is provided with displacement amount data I supplied from a displacement amount control device (not shown) or a keyboard (not shown).
N is divided by the unit change amount data U set in the unit change amount setting unit 101 to output a quotient S and a remainder A, and a field effect transistor or the like is used based on the quotient S. The digital displacement control means 104 which outputs the switching operation command SW to the switch circuit 103 and drives the number of digital displacement elements corresponding to the quotient S, and the relational data HD between the voltage applied to the analog displacement element and the displacement amount thereof. Applied voltage calculation means 106 for calculating the voltage to be supplied to the analog displacement element from the set relational data HD from the analog displacement-voltage setting means 105 and the analog displacement amount based on the remainder A, and outputting the applied voltage data VD; Variable displacement type analog displacement element driving power supply 107 for supplying a corresponding voltage based on the voltage data VD, and digital displacement element driving Consisting of the power supply 108..

The unit change amount data U in the unit change amount setting means 101 and the relational data HD in the analog displacement-voltage setting means 105 can be easily changed by input means such as a keyboard (not shown). I am configuring.

Therefore, when the required displacement amount is given, the required number of digital displacement elements are driven, and the required voltage is supplied to the analog displacement element, so that the desired displacement can be automatically obtained.

[0029]

As described above, in the laminated actuator according to the present invention, the digital displacement element or the laminated element thereof that produces a predetermined displacement amount by the phase transition and at least the displacement amount of the digital displacement element can be continuously varied. Since the displacement element is laminated, high displacement accuracy can be obtained over a wide displacement range. Further, it is possible to obtain a wide range of displacement just by combining the digital displacement element and the analog displacement element.

[Brief description of drawings]

FIG. 1 is a schematic structural diagram of a laminated actuator according to the present invention.

FIG. 2 is an explanatory diagram showing a schematic structure of a digital displacement element and its displacement characteristics.

FIG. 3 is an explanatory view of compound displacement of the laminated actuator according to the present invention.

FIG. 4 is a graph showing a specific example of displacement characteristics of the laminated actuator according to the present invention.

FIG. 5 is a schematic structural diagram of a monolithic laminated actuator according to the present invention.

FIG. 6 is a schematic structural diagram of a displacement memory type laminated actuator according to the present invention.

FIG. 7 is a block configuration diagram showing a specific example of a power supply drive control device for a laminated actuator.

[Explanation of symbols]

 1,40,70 Multilayer actuator 2,41,71 Multilayer digital displacement element 3,60 Analog displacement element 5,108 Digital displacement element drive power source 6,107 Analog displacement element drive power source 20,50,80 Digital displacement element 42 Multilayer Analog displacement element 90 Digital displacement element recovery power supply

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[Procedure amendment]

[Submission date] October 18, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

As the analog displacement element 3, a displacement element body 3a made of a piezoelectric material such as PZT and provided with electrodes 3b and 3c is used. The analog displacement element 3 is
It may be used as the laminated structure shown in FIG. Each electrode 3
b and 3c are connected to the positive and negative power source output terminals of the variable displacement type analog displacement element driving power source 5, respectively.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

[0029]

Layered actuator according to the invention, as described above, according to the present invention comprises a digital displacement element or a laminated element produces a predetermined displacement amount by a phase transition, an analog displacement element can be continuously varied Displacement amount Because I laminated
High displacement accuracy can be obtained over a wide displacement range. Further, it is possible to obtain a wide range of displacement just by combining the digital displacement element and the analog displacement element.

Claims (2)

[Claims] 1. A digital displacement element that is made of a piezoelectric / electrostrictive material that undergoes a phase transition from an antiferroelectric phase to a ferroelectric phase when an electric field is applied and that produces a predetermined displacement amount, or a laminated digital in which the digital displacement element is laminated in the displacement direction. A displacement element and an analog displacement element made of a piezoelectric material or an electrostrictive material and capable of being displaced to at least the predetermined displacement amount according to an applied electric field are laminated in the displacement direction of each displacement element. Multilayer actuator. 2. A digital displacement element made of a piezoelectric / electrostrictive material having a displacement memory effect by causing a phase transition from an antiferroelectric phase to a ferroelectric phase when an electric field is applied, and a piezoelectric / electrical element that is analogly displaced by application of an electric field. A laminated actuator characterized by laminating an analog displacement element made of a strained material in a displacement direction.